LVM thin volume explained

Written by Gionatan Danti on . Posted in Linux & Unix

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Creative snapshots use

While snapshots are primarily used to create a point-in-time, read-only copy for backup purpose, they really are read-write objects. Their read-write nature can be used in more creative manners, for example to create differential images starting from a single, common template.

Both normal LVM and thin snapshots can be used for this scope, however thin snapshots provide the following benefits:

 dynamically allocated space: the snapshot will be as large as how much data you throw at it

 much lower risk of filling the snapshot volume: as the assigned space is dynamically managed, you don't risk to under-sizing your snapshot volumes

 higher speed: the entire metedata handling and dm-targets are designed to give higher performance

 above all, eventual updates on the original volume (eg: template updating) will not destroy you I/O speed as happens with a multi-snapshotted normal, original volume.

The main thin snapshot drawback is the inability to limit their maximum size: if you really, really, really need to set an upper cap on snapshot size, you had to use normal LVM snapshots.

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